THE SUITABILITY OF AMEKICAN WOODS FOR PAPER PULP 21 
birches, hard maples, gums magnolias, Ohio buckeye, butternut, and 
mangrove are rather difficult but are within the realm of profitable 
utilization. Of the ring-porous woods chestnut, after extraction, and 
the elms are fairly easily pulped and bleached. Unextracted chest- 
nut, however, yields a pulp which is very inferior and very difficult to 
bleach. Common catalpa, hackberry, and white ash are rather 
difficult; sassafras, red and white oak, mockernut hickory, and black 
locust are very difficult. 
BARK DISPOSAL 
In considering the availability of various species for paper pulp the 
question of the utilization of the bark removed in the preparation of 
the wood naturally occurs. The feasibility of such utilization 
depends to a very large extent on local conditions, and each species 
and locality should be studied independently. Attempts to make 
use of this waste have met with considerable success in a number of 
cases. The most obvious means od utilization is as fuel, and at many 
mills it is found that the burning of the bark supplements the fuel 
supply to an appreciable extent. This is especially true if the bark 
is obtained from knife barkers or, in case the wood is barked wet in 
drum barkers, if as much water as possible is removed by means of a 
press before feeding to the furnaces. The barks from some species, 
such as hemlock, contain sufficient tannin to justify recovery of the 
latter by means of water extraction before burning. Extracted hem- 
lock tanbark has also been found a suitable material for use with rags 
for the manufacture of roofing felt, and considerable quantities have 
been used for that purpose. Redwood bark is so utilized on a 
commercial scale. 
Experiments with bark from the southern pines indicate that satis- 
factory roofing felt may be made with it by adding enough sulphate 
pulp from the same wood to give the required strength for passing 
through the impregnating bath. Spruce bark has been used as a por- 
tion of the furnish in the manufacture of board and cheap wrapping 
papers, such as car liner. Balsam fir and spruce barks have been used 
in finely shredded form in the manufacture of heat-insulation material. 
SUITABILITY OF INDIVIDUAL SPECIES FOR PULPING 
Descriptive summaries dealing with the pulping characteristics of 
various species under one or more of the various processes are given 
on pages 25 to 65. These summaries include brief statements about 
names of species, their range, specific gravity, and fiber length. 
The information on names and range is based on the revised 
" Check List of the Forest Trees of the United States," by George 
B. Sudworth (United States Department of Agriculture (Miscel- 
laneous Circular 92.) 
ESTIMATION OF PULPING VALUE 
All statements appearing in the summaries as to yields and quality 
of pulp and consumption of bleach are to be regarded as estimates 
of results to be expected under commerical operating conditions. In 
arriving at such estimates the writers have considered, (1) under the 
chemical pulp, the results of a limited number of laboratory tests on 
each species — usually not more than two or three for each pulping 
process — the data for which are recorded in Tables 6 to 12, and, under 
